Microbial Degradation of Chlorsulfuron in Soil under Laboratory Conditions

The degradation of chlorsulfuron was investigated in sterilized and un-sterilized soils (pH 8.2) spiked at 40 μg a. i. ha⁻¹ (40 ppb) under laboratory conditions at 25°C and a moisture content corresponding to field capacity using maize bioassay. Degradation data in the two soils did not fonow first order kinetics. Degradation of chlorsulfuron was faster in un-sterilized soil than in sterilized soil, demonstrating the importance of microbes in breakdown process. Half-life of chlorsulfuron was 93 days in unsterilized soil, whereas it was 120 days in sterilized soil. This study shows that if chlorsulfuron is applied at recommended rate of 20 g ha⁻¹ (10 ppb) then risk of residual carry over to succeeding crop of maize is possible.